Parallel Tree Traversals for Soft-Output MIMO Detection Using Multiple Bit Flippings

The Layered Orthogonal Lattice Detector (LORD), developed by Siti, et al., is a famous soft- output detector for the MIMO system. It proposes to compute bit log-likelihood ratios (LLRs) in parallel for bits in each layer of the transmitted MIMO signals and therefore can achieve high throughput rate. However, one of its disadvantages is the high complexity for high-order modulated symbols. Combining the Schnorr-Euchner enumeration and bit flipping scheme, we propose to enumerate the lattices at the top layer in a new way. Our proposed detector can avoid the bit vacancy problem and is demonstrated to outperform the fixed-complexity soft-output detector. We also report the hardware implementation results for our proposed detector, showing that our detector is practically feasible.